rydan

Looking to use an arduino or similar board for some trial&error logic tests in a product we're working on. Problem is, it's an industrial product using 24V signal level, and not 5V. Question is, is there an Arduino or similar out there that work with 24V instead? Is there any ready made arduino shield for working with 24V signals?

I realize I can use voltage dividers or similar on inputs and 5V relays on outputs, but then it's not quite as quick and handy anymore. Any ideas?

One way to tackle this is with a solid state relay board (relay rack), and a bunch of IDC5 relays (Gordos, Grayhill, Opto22, ...). These relays will convert the 24V signal into 5VDC, while keeping the circuits optically isolated (ie very little chance on the 24V frying your arduino). You can get deals on these boards on ebay from time to time. Some boards have an IDC connector, others have edge connectors (like PC-cards). I guess you could solder wires on the edge connector and pull them straight to your arduino. I have not tried input DC relays thsi way, but am running 4x24=96 output relays through a tiny 8x10cm board that carries 12 shift registers 74HC595 and 4 IDC50 connectors. Works well.

I believe you can feed your 24 volt logic levels (or any higher DC voltage for that matter) directly into the arduino provided you use input resistors to limit input current to less than 1ma. So as a provisional value I'd suggest, for 24 volts inputs, using 33k minimum.

As to outputs, you can use 5 volt relays (250ohm coils minimum) as an interface to your external circuits.

feed your 24 volt logic levels (or any higher DC voltage for that matter) directly into the arduino provided you use input resistors to limit input current to less than 1ma. So as a provisional value I'd suggest, for 24 volts inputs, using 33k minimum.

As to outputs, you can use 5 volt relays...

I may be wrong about this being wrong (!)... but don't act on the suggestion without waiting a bit to see if anyone else responds to the post?

The second part might be okay if you add a few "buts". There is a limit to how much currend can safely flow through a single I/O pin, and another limit to how much current you can allow to flow through the whole chip. You might well be able to have one 5v coil relay driven by the Arduino... but probably not ten.

Well I wouldn't recommended. The arduino (like most cmos circuitry) has internal clamping diodes for static protection but the current is very limited. Even at 1mA you are stressing the device. I prefer to use either external clamping diodes:-http://www.thebox.myzen.co.uk/Tutorial/Protection.htmlor much better feed the signal into the base of a transistor first.

I believe you can feed your 24 volt logic levels (or any higher DC voltage for that matter) directly into the arduino provided you use input resistors to limit input current to less than 1ma.

I would never trust that conditions remain "ideal" enough on a truck (or any similar industrial environment) to rely on just OHMS LAW to protect delicate input pins when the potential for error is so high and in this case the solution is screaming for "isolation" in the form of opto-couplers or solid state relays/standard relays.

my analogy again: I would so rather lose a finger than blow my brains out if something goes amiss.

AltairLabs

board for some trial&error logic tests in a product we're working on. Problem is, it's an industrial product using 24V signal level,

Not clear if Arduino is used by you to *test an industrial product* of if Arduino will become *part of an industrial product*. If the latter, then its imperative that your solution be rugged and reliable and maintainable, in whihc case pubdc has the best answer. Really the only answer appropriate for an industrial product.

If you re just using Arduino yourself for in-house testing then many of the fine ideas expressed above will work. Took me a minute to find this but Grumpy_Mike provided this to another post, its relevant to you too if you wanna "roll yer own" rather than use standard industrial I/O like opto-22.